I put up a post a few weeks ago about my 400ex not starting. Thought it was too cold but it was really becuase the spark plug was bad. I cleaned it off before and when i rode last time, and checked it today, there was carbon all over it. I got a new spark plug today and replaced it. It started right up. My question is, why is it that carbon is building up on the spark plug so fast? Is it too rich? Is it burning oil? Need some answers. Thanks

 

it sounds like you are runing rich and if there is some blue smoke comeing out of the exaust you are burning oil

 

how can i make it more lean? It has the stock pipe, stock jets, and everything else. I have a K&N air filter. I will try and clean it again today and spray some throttle body cleaner in there. Any suggestions?

 

I would take the plug out and poor seafoam into the chamber.enough to fill it. Turn the motor over a few times slowly. Make sure the switch is off. let it sit for awhile. maybe 20 minutes. or so . Do this with the engine warm but not hot. shut the gas off too. After it sits awhile turn it over and blow all the seafoam and chunks of carbon out. put the plug back in and run it hard. It will probably foul the plug but thats okay you need to blow the loose carbon out. check the plug and repeat as neccesary.